The campaign, called 'Time's Up', aims to protect women from sexual harassment across all areas of the workforce - especially those who are particularly vulnerable or don't have the funds to seek legal help.

The move follows an outpouring of sexual allegations made against the likes of movie mogul Harvey Weinstein.

Natalie Portman, Emma Stone and Reese Witherspoon are backing the initiative, which includes a $13 million fund for less-privileged women to defend themselves in court, paid for by the stars.

"Harassment too often persists because perpetrators and employers never face any consequences," an open letter signed by the 300 women reads.

"This is often because survivors, particularly those working in low-wage industries, don't have the resources to fight back.

"We particularly want to lift up the voices, power, and strength of women working in low-wage industries where the lack of financial stability makes them vulnerable to high rates of gender-based violence and exploitation."